1. Field of the Invention
This invention relates generally to video cameras, and more particularly is directed to miniaturized or small video cameras.
2. Description of the Prior Art
Video cameras are generally classified according to their intended use, for example, broadcasting station use, personal or consumer use and industrial use. Those video cameras intended for personal or consumer use and industrial use are desirably reduced in size for increasing the range of applications thereof.
In existing small video cameras, a front body for supporting a solid-state image pick-up element is fitted on an end of a main casing, and a plurality of base plates on which various electronic elements and components are mounted for constituting a drive circuit of the solid-state image pick-up element are relatively closely packed within the main casing. In the existing small video cameras, the base plates are usually fixed to the main casing by respective screws, or only one of the base plates is thus fixed to the main casing and the other base plates are, in turn, secured to the fixed base plate by connectors or the like. However, the use of screws, as aforesaid, for securing one or more base plates within the main casing undesirably limits the extent to which the sizes of such base plates may be reduced. More specifically, on shown on FIG. 18, each base plate 100 to be secured to the main casing by screws has to be formed with a through hole 101 in each corner portion of the base plate, with each such through hole 101 being spaced at least a predetermined distance d from the edges of the plate 100 which intersect at the respective corner. The distance d must have at least a predetermined value in order to provide sufficient strength, and further to ensure that the head 102 of each screw extending through a hole 101 at a corner of a base plate will not extend beyond the edges of the base plate. Thus, it will be seen that each screw used for securing a base plate 100 to the respective casing makes a respective substantial area of the base plate unusable for the mounting of electronic parts and components. Therefore, at a time when the sizes of electronic parts and components are being substantially reduced so as to make possible a reduction in the overall size of the base plate, the ratio of the area of the base plate required to be reserved for the screws securing the same to the casing relative to the area of the base plate available for the mounting of electronic parts and components becomes undesirably greater.
Furthermore, in the existing video camera construction described above, since at least one of the base plates is fixedly secured to the main casing by screws, vibrations and impacts to which the main casing is subjected are directly transmitted therefrom to the base plates and to the electronic elements thereon which are known to have relatively weak resistance to vibrations and impacts. This problem is made more acute as the volume of soldering employed is decreased with the reduction in size of the electronic parts and components. The reduced amount of solder used for making connections causes the latter to be more susceptible to failure when subjected to vibrations and impacts. The foregoing leads to an undesirable decrease in the reliability of video cameras as the size thereof is substantially reduced.
Further, in existing small video cameras, the front body for supporting the solid-state image pick-up element has a passage of circular cross-section extending therethrough for accommodating an optical path, and such passage also contains a picture frame plate, an optical filter and a cushioning member disposed in the order named in advance of the image pick-up element. The picture frame plate 13' is shown on FIG. 19 to have a generally circular periphery corresponding to the circular cross-section of the passage in the front body and is formed with a rectangular opening or window 13a having an aspect ratio, for example, 3:4, which is the same as the aspect ratio of an image pick-up plane of the solid-state image pick-up element. The purpose of the plate 13' is to frame the picture projected on the image pick-up element by avoiding the impingement of unnecessary light on the image pick-up element, and also to support the optical filter at the front face thereof.
The development of solid-state image pick-up elements has progressed to the point where the size thereof is considerably reduced, with the ratio of the area of the pick-up plane to the total area of the front face of the pick-up element being quite large. In view of the foregoing, it is reasonable to expect that, for reducing the overall size of the video camera, the diameter of the passage in the front body which accommodates the optical path will be reduced to the outer diameter of the solid-state image pick-up element. Of course, in that case, it is necessary to correspondingly reduce the diameter D.sub.1 of the circular outer periphery of the picture frame plate 13'. Since the ratio of the area of the pick-up plane to the total area of the circular front face of the image pick-up element is large, the rectangular opening or window 13'a in the frame plate 13' has to be similarly increased in size so that the plate 13 will not eclipse or cast a shadow on the pick-up plane. When that is done, the thickness d.sub.1 of the frame plate 13' at the corners of the rectangular opening or window 13'a is undesirably small so that the frame plate 13' is weak at those points giving rise to problems during manufacture and in use.
Referring now to FIG. 20, it will be seen that, in an existing small video camera, the main casing A' has a rectangular cross-section with the aspect ratio of that cross-section being approximately the same as the aspect ratio of the rectangular pick-up plane 16'a of the solid-state image pick-up element 16'. The front block assembly B' includes a front body 7' which defines the cylindrical passage or space 11' in which the picture frame plate 13' and the image pick-up element 16' are accommodated. The front body 7' is shown to have a rectangular front portion 8' corresponding to the cross-section of the main casing A', and to which the latter is secured by screws 12' extending from the opposite sides through holes in the front portion of the main casing A' and into tapped holes in the opposite sides of the front body portion 8'. It will be appreciated that dimension L'.sub.1 on FIG. 20 measured from the center of the cylindrical passage 11' to each side of the rectangular body portion 8' and main casing A' is the sum of the radius of the passage 11' and the depth of material of the front body 7' required to accommodate the respective screw 12'. The dimension L' extending diagonally from the center of the passage 11' to each corner of the rectangular cross-section of the main casing A' is obviously larger than the laterally extending measurement L'.sub.1. Thus, the interior of a pipe or other space into which the existing video camera shown on FIG. 20 can be inserted, and which is indicated by the dot-dash line X, must have a radius no smaller than the dimension L'. In other words, the pipe or other space X into which the video camera may be inserted has to have a diameter greater than the transverse dimension of the casing A' dictated by the diameter of the solid-state image pick-up element 16' and which would otherwise be sufficient for accommodating the base blocks and associated electronic elements needed to provide the drive circuit for the image pick-up element. Thus, the cross-sectional configuration of the main casing A' of the existing small video camera shown on FIG. 20 limits the extent to which the space required for accommodating such camera may be reduced.